Large-scale networks of hydration water molecules around bovine β-trypsin revealed by cryogenic X-ray crystal structure analysis
Large-scale networks of hydration water molecules around bovine β-trypsin revealed by cryogenic X-ray crystal structure analysis
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DOI：
10.1006/jmbi.1999.2795
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发表时间：
1999-06-11
影响因子：
5.6
通讯作者：
Nakasako, M
中科院分区：
文献类型：
--
作者：
Nakasako, M
在低温 X 射线衍射实验中研究了牛 β-胰蛋白酶的水合结构。选择具有不同分子堆积的苯甲脒抑制的酶的三种晶型来推断酶整个表面的水合结构。所有三种晶型的晶体结构在100 K和293 K下均以1.8埃的分辨率得到精化。100 K时酶周围的水合水分子数比293 K时大1.5至2倍，表明水合水的运动被冷却淬灭。特别是，在平坦和静电中性的表面区域，水合水分子数量的增加尤为显着。 100 K 下水合胰蛋白酶结构模型的水与蛋白质质量比和回转半径与溶液中蛋白质的其他实验技术获得的结果一致。水合水分子形成各种形状和尺寸的聚集体，一些聚集体甚至通过形成低聚排列覆盖疏水残基。此外，聚集体还形成了大规模的氢键网络。这些网络像拼凑物一样覆盖了胰蛋白酶的大部分表面，并机械地连接了酶的几个二级结构。通过合并三种晶型在100 K下的水合结构，引入水合水分子的分布函数来近似溶液中胰蛋白酶的静态水合结构。该功能表明，胰蛋白酶的带负电荷的活性位点倾向于容易暴露于本体溶剂。这一结果对于溶剂屏蔽效应和胰蛋白酶对带正电底物的识别很有意义。 (C) 1999 年学术出版社。
The hydration structure of bovine beta-tryysin was investigated in cryogenic X-ray diffraction experiments. Three crystal forms of the enzyme inhibited by benzamidine with different molecular packing were selected to deduce the hydration structure for the entire surface of the enzyme. The crystal structures in all three of the crystal forms were refined at the resolution of 1.8 Angstrom at 100 K and 293 K. The number of hydration water molecules around the enzyme at 100 K was 1.5 to two times larger than that at 293 K, indicating that the motion of hydration water was quenched by cooling. In particular, the increase in the number of hydration water molecules was prominent on flat and electrostatically neutral surface areas. The water-to-protein mass ratio and the radius of gyration of a structural model of hydrated trypsin at 100 K was consistent with the results obtained by other experimental techniques for proteins in solution. Hydration water molecules formed aggregates of various shapes and dimensions, and some of the aggregates even covered hydrophobic residues by forming oligomeric arrangements. In addition, the aggregates brought about large-scale networks of hydrogen bonds. The networks covered a large proportion of the surface of trypsin like a patchwork, and mechanically linked several secondary structures of the enzyme. By merging the hydration structures of the three crystal forms at 100 K, a distribution function of hydration water molecules was introduced to approximate the static hydration structure of trypsin in solution. The function showed that the negatively charged active site of trypsin tended to be easily exposed to bulk solvent. This result is of interest with respect to the solvent shielding effect and the recognition of a positively charged substrate by trypsin. (C) 1999 Academic Press.